Automatic positioning circuit for cathode-ray tubes



arch l, 1949. w. TQDD I.

AUTOMATIC POSITIONING CIRCUIT FOR CATHODE-RAY TUBES Filed April 15, 19462 Sheets-Sheet l swEEP AND J36 SPREAD CONTROLLERS #35 24 so I$YNCHRONOUS VERTICAL AUTOMATIC DEFLECTION VERTICAL Q AMPLIFIERPOSITIONING 38 i 47 .b- HORIZONTAL 4 4 f 46 48 DEFLECTION cIRcuIT (swE EP) 29 7 i0 RHEOSTAT gwue/IWM/ WILLIAM TOD D 2.22 FIG.2.

March 15, 1949. w. TQDD AUTOMATIC POSITIONING CIRCUIT OR CATHODE-RAYTUBES 2 Sheets-Sheet 2 Filed April 15, 1946 mmm 2::E:2:: ==L

d) O N gin um W5LLIAM. TODD -&Q J1

mmm N uE Patented Mar. 15, 1949 AUTOMATIC POSITIONING CIRCUIT FORCATHODE-RAY TUBES (Granted under the act of March 3, 1883, as amendedApril 30, 1928; 370 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

"This invention relates to circuits for automatic positioning of imageson the screens of cathode ray tubes.

More particularly, the circuit comprises a network, the output of whichis used for so biasing the vertical deflection plates of a cathode raytube as to reproduce continuously on the oscilloscope screen the peaksof signals even if their amplitude varies so as to exceed the maximumdeflection voltage necessary for producing maximum height images on theoscilloscope screen. Stated differently, sometimes the amplitudes ofsignals impressed on the vertical defiection plates in class Apresentation of the signals, are too high for reproducing the entiresignal on the oscilloscope screen. When this is the case,' the signalpeaks will be completely ofi the oscilloscope screen and thus lostbecause the cathode ray beam will be deflected beyond the extremeboundaries of the screen. It is very Well known to provide a gaincontrol for an oscilloscope to decrease the amplitudes for reproducingthe entire signal within the boundaries of the screen. In the systemdisclosed by this invention such amplitude limiting would either impairor completely destroy the accuracy of the results, since the latterdepends on the comparison of the height of adjacent images reproduced onthe screen. Therefore, the conventional solution of this problem cannotbe used. The invention discloses an automatic vertical positioningcircuit which automatically depresses the position of the horizontalsweep line so that the unattenuated peaks of the signals would bebrought onto the screen and their bottoms chopped off. The circuit ofthis type is of special value where the sought information is obtainedby comparing the amplitudes or the height of visual images. When this isthe case, even a moderately slow acting automatic volume control circuitin the receiver would not perform the desired function since suchautomatic volume control circuit would automatically reduce theamplitude of some of the signals and therefore diminish, or wipe offaltogether, the difference in height of adjacent images with theconcomitant reduction in accuracy of the desired information.

The automatic vertical positioning circuit has an additional applicationwhich relates to the automatic positioning of the sweep line on thetransmitter.

oscilloscope screen so that it continuously coincides with the zeroreading on the vertical scale of the screen. Because of the electricalmemory of the intelligence channel using reactance coupling, this linehas a. tendency to deviate from its intended zero position when there isa change in amplitude or wave shape of impressed signals. When keepingof this line on the zero position is important for measuring theamplitudes of the reproduced images, it becomes desirable to have someautomatic means which would counteract the shifting of this line to anyother position.

The invention will be described in connection with a meteorologicalradio direction finder designed to operate as part of a system to securethe direction. and speed of wind. The obtained information is of valuefor meteorological purposes. While the invention is described inconnection with this specific radio system, it'is to be understood thatit has wider application as will become more apparent from thedescription of the invention.

The meteorological radio direction finders may be considered as aspecial application of the radar systems to meteorological use. The onlycomponent that is lacking is the transmitting channel since themeteorological radio direction finders receive their signals from aradiosonde or portable radio transmitter carried by a balloon.Therefore, in this case, the signal comes from the object itself, andthere is no necessity for transmitting an exploratory pulse forobtaining an echo. As a consequence there is no transmitting channel andno electrical echoes in the systems of this type. However, the receiverand the antenna array otherwise are essentially identical to those usedin the radar systems. The antenna is a double tracking or split patterntracking antenna, or, more specifically, the quadruple tracking antenna,two double tracking horizontally shifted lobes being used fordetermining azimuth, and two identical but vertically shifted lobes fordetermining elevations. This makes it possible to point the axis,perpendicular to the center of the plane of the antenna array directlyat the source of signals for determining the azimuth and elevation ofthe The range is computed from pressure data taken during the flight ofthe balloon and the function. of the elevation angle to'the balloon.

Before the use of radio tracking methods, almost all winds-aloftobservations were made by two methods. The first method, which is theoptical method, used a right angle telescope to observe, at one minuteintervals, the azimuth and elevation angles of a balloon during freeflight. These angles, together with an assumed rate of ascent, were usedto calculate the position of the balloon from minute to minute. In thisway the direction and speed of the wind at various altitudes iscomputed; however, no other meteorological information is possible. Thesecond method augments the optical method by tracking a balloon borneradiosonde transmitter with the theodolite, the radio equipment beingused only to obtain information on humidity, pressure and temperature.

The principal disadvantage of the optical methods is the limitationcaused by visibility.

Another disadvantage of. the first method is.

ascent rate is determined from pressure data taken during the flight ofthe balloon. The latter data is usually obtained through detection of asuperimposed carrier modulation.

As mentioned previously, the azimuth and elevation angles are determinedby means of split pattern tracking, the main lobe axis of the four lobespointing directly at the balloon transmitter when the heights of fourimages reproduced on the oscilloscope screen are all equal. With theadvent of the radio tracking method, it was soon discovered thattracking of the balloon is quite difficult at the higher angles ofelevation because of very pronounced variations in the intensity of thesignal reaching the receiver. This erratic fluctuation in the intensityof the signal is due to continuous swinging and erratic oscillations ofthe transmitting wire-antenna carried by the balloon radiosonde when theballoon is tossed about by varying air currents and sudden gusts of windwith the concomitant rotation of the transmitter about a vertical axiswhen the transmitter has a slightskew pattern the two phenomenacombining to produce marked amplitude variations. Sinceproper'orientation of the receiving antenna array is possible only whenthe position of the received signals remains fairly stationary on theoscilloscope screen or, in an extreme case, there is no totaldisappearance of the peaks from the screen, it becomes necessary toprovide some means, i. e.. the automatic vertical positioning circuit,for keeping the peaks of the signals continuously on screen even whenthe transmitter and its antenna are caused to rotate and oscillate byvarying air currents.

It is therefore an object of this invention to provide an automaticvertical positioning circuit for the oscilloscope of meteorologicalradio direction finders, this circuit automatically keeping the peaks ofthe images on the oscilloscope screen even when the signals reaching theradio direction finder experience violent intensity variations.

An additional object of this invention is to provide an automaticvertical positioning circuit for a cathode ray oscilloscope which makesit possible to reproduce the peaks of images of signals on theoscilloscope screen even when the amplitudes of these signals are suchas to produce, without the above-mentioned circuit, beam deflectionsbeyond the boundaries of the screen.

Still another object of this invention is to provide an automaticvertical positioning circuit for electrically counteracting the verticaldeflection of a cathode-ray beam in a cathode-ray oscilloscope in such amanner as to depress the bases of large amplitude signals when theyreach such large values as to produce, without such counteracting, thebeam deflections beyond the boundaries of the oscilloscope screen.

An additional object of this invention is to provide an automaticvertical positioning circuit whch is capable of keeping the position ofthe sweep line in class A presentation of images on the oscilloscopescreen at a predetermined position on the screen in spite of largevariations in the amplitude and duration of .intelligence signals,which, because of the inherent electrical memory of the intelligencechannel, tend to shift the position of the sweep line of! its normalzero position.

These and other features of the invention will be more clearlyunderstood from the following detailed description and the accompanyingdrawings in which:

Figure 1 is a block diagram of the radio direction finder;

Figure 2 is a schematic diagram of an automatic vertical positioningcircuit;

Figure 3 illustrates images appearing on an oscilloscope screen in thesystems of this type;

Figure 4 illustrates an approximate shape of the antenna lobes of theradio direction finder;

Figure 5 is a graphic illustration of the action of the automaticvertical positioning circuit;

Figure 6 illustrates modified connections of the automatic verticalpositioning circuit to the intelligence channel. 7

Referring to Fig. 1, it discloses a block diagram of a portablemeteorological radio direction flndei' with a balloon transmitter i0illustrated to the left of the finder. The radiosonde consists of ahydrogen-filled balloon [2 which carries transmitter Ill. The latter isprovided with an antenna ll, which is a half-wave-length wire suspendedfrom the transmitter. Transmitter l0 transmits a U. H. F.-C. W. signalillustrated by an arrow it, which is intercepted by an antenna Itprovided with four phased lobe positions W, X, Y, and Z. A cigar-shapedlobe pattern is obtained for each lobe position. This system is known asdoubletracking or split-pattern tracking; the principle of such trackingis illustrated in Fig. 4 for one component of direction; the sameprinciple is used for both azimuth and elevation tracking. The lobing iscontrolled by motor 42 through shaft 35. The array is arranged so it canbe rotated about both vertical and horizontal axes, which enables anoperator to perform the actual tracking of the transmitter.

The directivity pattern has a directional lobe which points in thegeneral direction of the transmitter. However, the lobe departs a fewdegrees (up-down or right-left) from a line drawn perpendicular to thecenter of the antenna plane, as illustrated in Fig. 4. The effectproduced on the antenna system of this kind by the incoming C. W. signalis as follows: If a wave front arrives along line AO it will inducemaximum signal voltage when the right-hand antenna lobe is effective;however, signals arriving at angles other than A-O will produce weakersignals. For example, a wave front arriving along line 3-0 would producea signal proportional to the lengthcassava of line C-O. The samesituation would exist it the transmitter position and antenna lobes werereversed. With a wave front arriving along line B- and the left antennalobe efiective, a maximum signal voltage would be induced. This isrepresented by line B-O. With the left antenna lobe efiective and thewave front arriving along line A-O, the signal would be much weaker. Ifa wave front arrives along line E-O and the two antenna lobes areswitched, the signal amplitudes will be equal.. This is represented bythe lobes intersecting at point'E and equal length of line E-O for bothlobes. The main lobes have been exaggerated for purposes of explanationand are not represented as the actual patterns. The output due to eachlobe from theantenna will be the same when the antenna array isperpendicular to the plane of the wave front in both azimuth andelevation.

Shaft 35 is connected also to sweep and spread controllers 36 whichcontrol a sweep circuit 38. The output of sweep circuit 38 is connectedto the horizontal deflection plates 40 and 4| of tube 21. Asynchronousmotor 42 is used for controls ling the lobing of antenna l8 and sweepcontrollers 36. avoid possible undulations in the traces on theoscilloscope due to slight differences between the power line frequencyand the frequencies generated by rotation of the switch. The sweepcontrollers initiate a saw-tooth wave sweep corresponding to each twosuccessive lobe positions of the antenna, alternate sweeps beingdisplaced by any known means for purpose of spread control. The resultis that every second horizontal sweep of the oscilloscope spot on thescreen begins from a point slightly to the right of the preceding sweepexcursion which produces the lateral displacement of images illustratedin Fig. 3. Each sweep traverses the oscilloscope screen while theantenna passes through two lobe positions producing two modulationpulses. pip 300 and one azimuth pip 302 are thus presented for eachsweep of the electron beam. The following sweep excursion traces thenext elevation pip 304 and azimuth pip 306 produced by amplified,demodulated, and finally impressed as a video pulse on a verticaldeflection amplifier 24. This permits the receiver output to be examinedon each lobe position of the antenna.

The output of the receiver, as presented on oscilloscope, thus consistsof a continuous series of pulses such as those illustrated in Fig. 3.These are impressed on the vertical deflection amplifier which uses atwin triode tube connected in a phase inverting circuit. Output signalsfrom the amplifier 24 are applied through blocking capacitors 44 and 46and conductors 22| and 29 to the vertical deflection plates 25 and 26respec. tively of the oscilloscope. Since the signals impressed oncondensers 44 and 46 are in phase opposition, the A. C. voltagedifference between deflection plates 25 and 26 is doubled, providinggreater deflection sensitivity.

One of the output circuits of the vertical deflection amplifier 24 isalso connected through a coupling condenser 41 and a conductor 32 to theautomatic vertical positioning circuit. This cir- Motor 42 is asynchronous motor to One elevation cuit automatically controls theposition or the traces on the oscilloscope screen through a conductor48, which connects its output to conductor 29. The automatic verticalpositionin rcuit automatically biases the deflection plates so that theposition of the tops of the four pulses 300, 302, 304 and 306, will tendto remain on the screen even when large amplitude changes take place inthe video signals impressed on the deflection plates 25 and 26. Ifreceiver saturation is reached. the amplitudes of all signals maytemporarily become equal should the orientation of the antenna array besuch as to produce receiver saturation on all four lobes. This keepingof the tops of the four pulses on the oscilloscope screen by theautomatic vertical positioning circuit is accomplished by shifting thesignal base line of the oscilloscope in synchronism with variations inaverage signal strength as illustrated by an approximate oscillogram inFig. 5. Since, as mentioned previously, the operator judges whether theantenna points directly at the transmitter l0 by comparing theamplitudes of the images illustrated in Fig. 3, it is obvious thatshifting of the signal base line 400 on the oscilloscope in synchronismwith the variations in average signal strength will have no effect onthe difference in the amplitude of the respective elevation and. azimuthsignals. Consequently, the sensitivity of the antenna array setting isnot impaired in any way by the automatic vertical positioning circuitbut is enhanced by presenting the difference in heights upon a magnifiedscale. The schematic diagram of this circuit is illustrated in Fig. 2.

Referring now to Fig. 2, the schematic diagram begins with a twin triode24, which corresponds to the vertical deflection amplifier 24 of Fig. 1;

it is connected to the output of receiver 22. In-

positive input signals 20! from the voltage amplifying stages ofreceiver 22 are appliedthrough blocking capacitor 200 to a vertical gaincontrol resistor 202 and then to the grid of the first triode. Negativesignals 203 of greater amplitude appear across plate load resistor 204,and are then applied through blocking capacitor 206 to a voltagedividing network consisting of resistors 208 and 2 l0. Thus a portion ofthe output signal from the first triode section is applied to the secondtriode grid, and appears amplified as a positive signal 2 across a plateresistor 212. The voltages appearing across resistors 2l2 and 204 areapplied through the blocking capacitors 44 and 46 to the vertical plates25 and 26 respectively of the cathode ray tube 21 where they produce thevertical deflections illustrated in Fig. 3. Thenegative signal from thefirst stage of am plifier 24 is also applied through condenser 41 to thecathode 2; of the first section of triode 30, which is connected as ahalf-wave rectifier, the cathode being grounded through a resistance 2l4, and the tied together grid and plate grounded through a resistance2l8. When cathode 2H} is driven negative by the signals impressed uponit by condenser 41, the first half section of triode 30 draws currentthrough grid resistor 2l8.- The latter is shunted with an integratingcondenser 226, the time constant of resistance-condenser combinationbeing adjusted so as to .provide proper average grid voltage for thesecond stage of triode 30. The voltage across this network is amplifiedby the second triode. As the signal amplitude increases, the platecurrent through plate load resistor 220 decreases, causing an increasein voltage across resistors 222 and 224,

which are connected to the vertical plate 28 of the cathode ray tubeover conductor 28. The voltage thus developed across resistances 222 and224 opposes the shifting in the tops of the traces caused by theincrease in the average amplitude of the signal, and it is this voltagethat acts as an electrical means for automatically keeping the tops ofthe four pulses on the screen even when the amplitude of the signalswould otherwise deflect the oscilloscope beam beyond the boundaries ofthe screen.

The time constant of the automatic vertical positioning circuit is thesum of the'normal time constant of the output circuit of the verticalamplifier and the R.-C. circuit consisting of resistancees 220, 222, 224and condenser 228. The amplitude of the bias voltage applied to thedeflection circuit is adjustable by rheostat 222, while its timeconstant is adjustable primarily by varying the capacitance of condenser228. In general, the time constants of the entire oscilloscopedeflection circuit are adjusted to conform to the repetition rate of thevideo intelligence and the period of the amplitude variationsexperienced in the course of average radio sondings.

This action of the automatic vertical positioning circuit is illustratedin Fig. where the negative signals 203 appearing in the output of thefirst stage of 24 are combined with the potential variations 500appearing across resistor 224 due to the action of the automaticvertical positioning circuit. It is to be noted that in Fig. 5 theamplitude of voltage wave 500 increases with the increase in theamplitude of the signals 203, and vice-versa. The net result isthat thepeaks of the signals 203 remain visible. The amplitude of the signalsactually impressed on the deflection plates is illustrated by thedifference in the amplitudes of the signal 203 and wave 500, thisdifierence being illustrated at 502. In practice the parameters of theautomatic vertical positioning circuit should be adjusted also so as tohold the images on the screen in spite of the push-pull action of thesignals 203 as well as 2| I.

Since the signals 2! I are impressed directly on the deflection plate 25without any control by the automatic vertical positioning circuit, theentire amplitude control must be accomplished by controlling thepush-pull action only through one side or end of this double-endedcircuit.

Thus the function performed by the automatic vertical positioningcircuit is to enable the operator to see a greater amplitude difierencein terms of actual greater linear distances between the peaks of theimages appearing on the oscilloscope screen. This is accomplished byimpressing the deflection voltages or. the deflection plates of theoscilloscope of such magnitude that if it were not for the automaticvertical positioning circuit, the peaks of the signals would becompletely oil the oscilloscope screen. The automatic verticalpositioning circuit however depresses the base line in such a mannerthat, in spite of the fact that the voltages impressed by the receiveron the oscilloscope are too high for their reproduction on the screen,the automatic vertical positioning circuit varies the position of thebase line so that the intelligence contained in the diflerence in theamplitudes is reproduced on the screen without any attenuation. In asense therefore the automatic vertical positioning circuit acts as adiiferential amplifier which amplifies very greatly the differences inthe amplitudes of the different phase-position signals. Hence the reasonfor. making the statement that the automatic vertical positioningcircuit enhances the accuracy of the Rawin" system by presenting thediiierence in heights of the intercepted signals upon a magnifled scale.

The disclosed automatic vertical positioning circuit has an additionalapplication in the oscillographic art which is illustrated in Fig. 6. InFig. 6 the automatic vertical positioning circuit is connected to upperconductor 22l rather than conductor 28, as it is the case in Fig. 2. theremaining connections of Fig. 6 being the same as those illustrated inFig. 2. The function performed by the automatic vertical positioningcircuit with this type of connection is as follows: it is quitecustomary, with type A presentation of images on the oscilloscopescreen, to use a screen which has a transparent calibrated scale mountedon the face of the tube. This screen is then used for measuring theheight or amplitude of the images appearing on the screen. The scaleusually has a zero line corresponding to the zero reading of thevertical deflection, and the biasing of the vertical deflection platesis adjusted by means of a potentiometer, such as a potentiometer 225 inFig. 2, so that the position of sweep coincides with the zero reading onthe Y scale. The parameters of the intelligence channel in theoscilloscope circuit, which corresponds to the channel including adouble triode 24, condensers- 44, 46, vertical deflection plates 25, 26,etc., can not have zero time constant since it is obvious that anyphysical condenser-resistance combinations will have some finite timeconstants. Stated difierently, any electrical circuit of this type has acertain electrical memory, and as the amplitudeand duration of thesignals impressed on the intelligence channel is varied, the eflect ofthis memory upon the position of the sweep line on the oscilloscopescreen is that it wanders from its zero position in response to thesevariations. The deflection of the sweep line {rom zero position isalways in the opposite direction to the direotion of increase inamplitude of the signals, 1. e., in the negative direction on theY-scale when the amplitude or the duration of the signals are on theincrease circuit. Therefore the polarity of the correction must beadditive with respect to the intelligence signal. Potentiometer 225, asa rule, is an adjustable potentiometer and it is used for restoring theposition of the sweep line to its zero position by manually adjustingthe position of the potentiometer arm. Such method of adjusting theposition of the zero line on the oscilloscope screen is quite tedious,and in some instances it is rather difllcult to follow the wanderings ofthe position of the sweep line with respect to the Y-axis withsufllcient degree of accuracy. When this is the case, all readingsbecome inaccurate. It is possible to apply the disclosed automaticvertical positioning circuit for automatic positioning of the sweep lineso that it remains continuously at zero on the Y-axis in spite of thememory eflect in the intelligence channel. For accomplishing thispurpose, the output of the automatic vertical positioning circuit isconnected to conductor 22l which impresses an automatically adjusted,variable positive biasing on the "deflection plate 25, which counteractsthe varying negative memory effect. The parameters of the automaticvertical positioning circuit are in this case adjusted in the samemanner as before by adjusting the setting of rheostat 222 and condenser228. The selected values would obviously be such asto counterbalance thememory eflect oi the intelligence channel. It is to be noted that 9 theautomatic vertical positioning circuit of the disclosed type isapplicable to intelligence signals whose amplitude variation has aperiod at least as long as several cycles of intelligence signal;otherwise, distortion of the intelligence signal presentation willresult.

In describing the automatic vertical positioning circuit in connectionwith its appl cation to the meteorological system and in illustratingits action in Fig. 5, it has been stated that the parameters of thiscircuit may be so adjusted that there may be a slight variation in theamplitude of the signals and in the amplitude of the images reproducedon the oscilloscope screen. The mode of operation of the automaticvertical positioning circuit however may be so adjusted it matches anygiven variation in the modulation of the signal, the only limitationbeing that the time constant be chosen to permit the desired correctingvoltage to operate on the cathode ray tube.

- The amplification of the automatic vertical positioning circuit maythen be adjusted to produce constant amplitude image on the screen ofthe oscilloscope. In the latter case the one extremity of all signals,i. e., the peaks, remain fixed on the oscilloscope screen.

While the invention has been described with reference to severalparticular embodiments, it will be understood that various modificationsof the apparatus shown may be made within the scope of the followingclaims.

I claim:

1. A cathode ray oscilloscope circuit comprising, a cathode ray tubehaving a screen and means for deflecting the electron beam within saidtube, a source of signals connected to said means, said sourceimpressing signals of varying-= amplitude on said means, a verticalpositioning to confine the peaks of said signals to said screen withoutaffecting the difierences in the amplitudes of said signals.

3. A cathode ray oscilloscope comprising a cathode ray tube having ascreen and means for deflecting the electron beam within said tube forpresentation of images on said screen, an intelligence channel connectedto said means, said channel impressing signal pulses of varying energycontent on said means, said varying energy content capable of producinga shift in the position of a sweep base-line on said screen because ofthe electrical memory of said intelligence channel, and a positioningcircuit connected with its input to said channel and with its output tosaid means, said circuit producing a voltage proportional to the meanvalue of said varying energy content and applying said voltage to saidmeans to counteract said shift thereby maintaining the position of saidbase-line fixed on said screen during the variations in the energycontent of said signal pulses.

4. A cathode ray oscilloscope comprising, a cathode ray tube having ascreen, a Cartesian coordinates scale on said screen, opposing means inquadrature for deflecting the electron beam within said tube along saidcoordinates, a sawtooth oscillator connected to one pair of opposingmeans for deflecting said beam along X-axis for producing a base line,an intelligence channel connected to the other pair of opposing meansfor deflecting said beam along Y-axis, said channel impressing signalsof varying energy on said circuit responsive to the strength of saidsignals having beam-deflecting means, said means being.

connected to said receiver for presentation of said pulses on the screenof said oscilloscope, and a vertical positioning circuit connected tosaid receiver and to said deflecting means, said circuit responsive tothe mean amplitude of said video pulses to vary the mean voltage of saiddeflecting means to counteract the deflections of the cathode ray tubewhen the amplitudes of said signals exceed full-screen deflectionvoltage of said tube means, said varying energy capable of producing ashift along the Y-axis in the position of said base-line with respect tosaid scale because of the electrical memory of said intelligence channeland a corresponding shift of images on said screen, a rectifierconnected to said channel and having an integrating network in itsoutput, an amplifier connected to said network and having an integratingnetwork of its own in its output circuit, and a connection between thelatter network and said means, said latter network producing a voltagethat is applied to said means to maintain said base-line in a constantposition with respect to said scale.

I WILLIAM TODD.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 1,951,036 Parker Mar. 13, 19342,237,651 Bruche Apr. 8, 1941 2,312,761 Hershberger Mar. 2, 19432,358,545 Wendt Sept. 19, 1944 2,405,930 Goldberg et al Aug. 13, 19462,414,537 Lakatos Jan. 21, 1947

